1. Field of the Invention
This invention relates, in general, to the field of ophthalmic surgical systems and in particular to a method and system for supplying and controlling irrigation fluid and suction pressure for aspiration flow to be supplied to a surgical instrument for extracapsular removal of a cataract from an eye.
2. Description of the Prior Art
In general, removal of a cataract from an eye involves either extracapsular or intracapsular techniques. Removal of the lens and its outer covering, the lens capsule, is known as intracapsular removal. Extracapsular removal of a cataract involves cutting away the anterior portion of the lens capsule which serves to expose the lens and then the cataract and the cortex may be removed.
The actual removal of the lens and the cortex is accomplished a number of ways. In U.S. Pat. No. 3,857,387 (1974), the inventor utilizes ultrasonic vibration to fragment hard cataracts and to gently wash out the fragments through a corneal incision in the eye, utilizing gravity-fed irrigation fluid flow. Thus, the irrigation fluid flow serves to keep the eye inflated and to remove the fragments. The object of this art being to eliminate the complexities (complex electronic and hydraulic equipment) introduced by aspiration of the emulsified lens while maintaining high surgical success rates.
In U.S. Pat. No. 3,732,858 (1973), by Anton Banko, apparatus is disclosed having a pair of movable jaws to sever material, such as portions of a lens, as the jaws are moved relative to each other. The severed material is then contained within a passage incorporated in the movable jaws and subsequently aspirated from the eye by suction forces. The disclosed movable jaws include a generally tubular outer member having a rotatable inner member which in combination define cutting edges. In operation, the lens is forced against the jaw portions which is then severed by the shearing action of the jaws and removed through the passageway which is vented to the atmosphere.
In another method, in U.S. Pat. No. 3,589,363 (1971), Anton Banko discloses apparatus for removing a cataract comprising a handpiece or instrument having an operative tip capable of vibrating at ultrasonic frequencies and having both a source of fluid and a pump whereby particles of the lens are severed utilizing ultrasonic vibrations and dispersed within the fluid and withdrawn from the operating site by the pump.
Wallach, in U.S. Pat. No. 4,024,866 (1977), discloses still another method, whereby a pulsating high velocity liquid jet is directed at an object such as a lens, disintegrating the same into small particles which are removed by sucking the fluid entraining the particles from the operating site.
In an even further method, the anterior capsule is cut by an appropriate instrument thereby exposing the lens. The nucleus of the lens, if any, is dislodged from the lens into the anterior chamber of the eye and is subsequently removed through an opening at the limbus. The remaining cortex of the lens is then sucked from the eye by a balanced combination of irrigation and aspiration flow through a double-barreled needle inserted into the eye at the incision at the limbus. The above-noted method and the apparatus associated therewith is more completely described in U.S. patent application filed 10/12/79, Ser. No. 6/84,180.
It cannot be stated with certainty as to which method or combination of methods of removing cataracts is in most widespread use today. In all probability, intracapsular removal of cataracts, whereby both the lens and the entire capsule covering the lens are removed as a unit, is the most prevalent. However, the use of ultrasonic vibrations (with either extracapsular surgery or intracapsular surgery) and the intracapsular method using suction to remove soft cataracts and cortex are extensively used. And, both of these methods are most often accompanied by the use of both irrigation flow and aspiration flow. The former flow generally being used to maintain the shape of the anterior chamber of the eye during the operation; while the latter flow is used to remove soft cataracts (for example, in children) and cortex as well as emulsified portions of hard cataracts. With these methods, therefore, it is necessary to have a first fluid flow system for purposes of irrigation and a second fluid flow system for asiration. In many systems, both the irrigation flow and aspiration flow are combined in one overall system.
As may well be expected, the fluid flow systems utilized with cataract surgery have undergone significant transformations. Indeed, in early cataract surgery (other than total removal of the lens and the capsule) many failures were attributable to the lack of adequate flow systems. It is now realized that it is imperative to maintain the shape of the eye and during the operation. Uncontrolled collapse of the shape of the eye almost always resulted in failure. Irrigation flow to the eye maintains the shape of the eye, but it must be properly controlled so as to prevent both underpressure and overpressure. Similarly, aspiration flow must be precisely controlled so as not to cause unwarranted evacuation of the fluid within an eye and so as not to cause an operating surgeon to remove portions of the eye not intended to be removed. Unfortunately, an operating surgeon's mechanical skill is not necessarily synonymous with his surgical skill. Fluid flow systems which require a high degree of mechanical skill are understandably highly undesirable. Even the best and most qualified surgeons cannot totally overcome deficiencies in mechanical equipment. Simplified, easily controllable, and reliable fluid flow systems are, therefore, a necessity in cataract surgery.
An example of a relatively early prior art fluid control system is disclosed in U.S. Pat. No. 3,589,363 (1971), by Anton Banko. In this teaching, the problem which still exists today, is succinctly stated to be that an equilibrium condition must exist at the operative site between the irrigation flow, the aspiration flow, and the leakage flow past the incisions. In a sense, this equilibrium condition is self-adjusting. For example, for a given aspiration flow rate, an increased irrigation flow rate will result in a higher leakage rate past the incision. While such a condition might be said to be "balanced", it is not desirable because of the high leakage rate past the incision. Thus, a properly balanced equilibrium condition is one whereby there is no overpressure or underpressure in the eye, there is not too high or too low of an aspiration flow rate, and there is not too high a flow rate past the incision. In attempting to achieve such a balanced equilibrium, the above, last-stated prior art disclosed separate irrigation and aspiration flow systems. The irrigation flow being variably controlled by a switch which regulates the pressure of the irrigation fluid supply. The aspiration flow being controlled by a vacuum pump and a number of solenoid valves which in combination provide an unspecified but constant suction force (with no flow at the operating tip) or an unspecified but constant pumping flow from the operating tip.
In 1974, in U.S. Pat. No. 3,812,855, Anton Banko disclosed a relatively sophisticated system for controlling pressurized irrigation fluid and suction pressure for aspiration flow for use with a single handpiece for removing cataracts. This system provides a great degree of versatility and adjustability in supplying a pressurized fluid (irrigation flow) with or without suction pressure--and, therefore, aspiration flow--being applied. The disclosed system also provides for reversing the flow to the handpiece to eject unwanted material which might clog the instrument. Since a positive pressure pump is utilized to pressurize the irrigation fluid, an adjustment by a hand valve allows for a change in the irrigation fluid flow rate. Similarly, the suction pressure for the aspiration flow is controllable but now by two valves. Also, a controller is used to prevent too high a suction pressure. In practice, it has been found, however, that such a system is too complicated and requires a high degree of mechanical ability to be properly operated.
In U.S. Pat. Nos. 4,019,514 (1977) and 3,920,014, Anton Banko again disclosed systems for controlling the infusion of fluid to and the evacuation of fluid and material from an operating field such as an eye. In these patents, the inventor recognizes the complexity of his prior teaching and attempts to simplify that system while maintaining the same operating or functioning modes. Again, sophisticated and versatile systems are attained; but still again, there is a great degree of complexity.
U.S. Pat. No. 3,857,387 (1974) discloses a method of removing cataracts using ultrasonic vibrations and gravity flow of irrigation fluid. Aspiration flow is not used. The inventor, in this teaching, relies on a flow past the incision--described as gentle lavage flow--to expel fragmented portions of the lens from the eye. Thus, he achieves a very simple system which involves only irrigation flow which is controlled by a hand-operated valve. While the simplicity of this system is intriguing, it is limited to cataract removal using ultrasonic vibrations and no aspiration flow. It would, therefore, not be applicable to the instant method of cataract removal which does utilize aspiration flow to remove the remaining cortex of hard cataracts.
Anton Banko, in U.S. Pat. No. 4,007,742 (1977) again addresses the problem of simplicity of operation and control in providing an irrigation and aspiration flow system. In this teaching, Banko employs gravitational forces to provide irrigation flow to the eye. The rate of flow being regulated by adjusting the height of a bottle containing the infusion fluid relative to the height of the operation field. In this system, a constant displacement pump of the peristaltic type is used to aspirate fragmented portions of the lens. Fragmentation being accomplished by the rotating action of a twist drill within a cylindrical housing an opening at the operative end and through which the twist drill extends. Variations in the flow resistance through the operative instrument due to the continuously changing effective viscosity of the effluent flow is accommodated by volumetric changes in the flexible exit flow lines (tubing shrinks) and the "vacuum" forces created by the constant displacement pump.
Considering the numerous attempts to provide fluid flow systems for use with cataract removal surgery, it is apparent that there still exists a need for a simplistic but effective system. Accordingly, it is an object of the present invention to provide an irrigation-aspiration fluid flow system for use with extracapsular extraction of cataracts which does not rely upon fragmentation or emulsification of the lens of the eye.
Another object of the present invention is to provide a simplified surgical fluid flow system which requires a minimum of mechanical ability to operate in an effective manner.
A further object of the invention is to provide an aspiration fluid flow system which is powered by a vacuum pump.
A still further object of the present invention is to provide an irrigation-aspiration fluid flow system for use with cataract surgery which is electronically operated and controllable by the operating surgeon during the surgery.
Another object of the invention is to provide a surgical fluid flow system which is capable of operating in separate irrigation, irrigation plus low aspiration, and irrigation plus high aspiration modes and which modes of operation are readily discernible to the operating surgeon.
Still additional objects and advantages of the present invention will become more apparent upon reference to the following specification and annexed drawings.